The frequency bandwidth of electromagnetic waves used by the mobile phone is from 700 MHz to 2.5 GHz and the wavelength is from 43 cm to 12 cm. The electromagnetic waves generated by mobile phone are radiated into the space through body after being absorbed into the body at relative permittivity of more than 80 in the shape of length or perimeter near the wavelength that easily gets resonated.
The wavelength at frequency near 1 GHz used during call is from 20 to 40 cm. The fact that perimeter of head of an adult is of the length near the wavelength and the relative permittivity is high are combined due to which majority of the electromagnetic waves radiated during the phone call when the phone is at the ear are radiated into space through the head. The wavelength is less than 20 cm at the bandwidth of more than 1.5 GHz. However, length of the part that easily gets resonated in this frequency region is selected from the structure of head and waves are radiated into the space through this part.
The electromagnetic waves radiated from head or hand and arm are received at a distant base station. This time, the physics rule that stipulates the radiation of electromagnetic waves from hand and arm to the base station is far field condition with wavelength of more than 70% namely from 14-28 cm or more and design of wireless device is generally done according to this condition.
In the dipole antenna of the part that sends and receives electromagnetic waves, two metal rods of ¼th wavelength are arranged in straight line in long axis direction and input or output are connected to one end of the 2 metal rods which is called as feeding point and the other end is connected to the earth terminal. The feeding point and earth point are on the sides near end of each of the two earth rods. The total of two metal rods becomes ½ wavelength. If transmission of dipole antenna is given as example, long axis of metal rod is taken as center and electromagnetic waves are radiated in circular shape. Here, if metal rod is arranged parallel to dipole antenna little shorter than ½ wavelength by separating about ¼ wavelength, electromagnetic waves incline towards the newly installed metal rod direction due to circular shape of radiation pattern and shows directional characteristics. This is the theory of Yagi antenna and the newly added metal rod is called as waveguide. The electricity strength of electromagnetic waves on waveguide side becomes about double. However, theory and effect of this waveguide is far field condition.
In the frequency range of 700 MHz-2.5 GHz used in mobile phone, frequency range that can be sent and received by a single dipole antenna is about 5% as against the central frequency and hence, in a single dipole antenna, only a part of bandwidth used for mobile phone is covered.
Furthermore, physics rule that stipulates the electromagnetic waves in the region where distance from antenna is less than 70% of the wavelength is near field condition and it becomes remarkably below 10%. If the distance between hand holding the mobile phone or head and the mobile phone is 1 cm, it becomes 3% at 1 GHz frequency used by the mobile phone and 6% at 2 GHz. Therefore, the part of antenna that controls electromagnetic waves between head or hand must be designed according to the near field condition.
In the technological field of wireless communication, main point is placed where electromagnetic waves fly up to the distant place. Hence, design of system containing antenna is based on the far field theory. Even in case of using waveguide to improve transmission and reception characteristics, antenna and waveguide are integrated to form an antenna system and design is done based on far field theory using waveguide as a new radiation source of electromagnetic waves. Similar is used even in mobile phones. Antenna system is used with the aim of miniaturizing tip antenna using dielectric body having low specific permittivity loss of less than 5. However, telecommunication with base station that is the target of antenna design of mobile phone is designed according to far field condition. The fact that spatial impedance of antenna is constant regardless of distance is also combined, and design of antenna of mobile phone is done according to far field condition and near field condition is ignored. According to near field condition, magnetic field and electric field generated in antenna become function of distance and design becomes complex due to major change in impedance.
Patent literature 1 relates to the part that aims at reducing radiation exposure of electromagnetic waves to head of the person using the mobile phone by installing a part that has wave directing function and reflection function that is externally attached to the mobile phone. Regardless of head and hand of the user being at a distance of about 5% of the wavelength of the electromagnetic waves used by the mobile phone, design is done by using basic theory of controlling electromagnetic waves based on the far field condition without considering this distance.
Namely, patent literature 1 focuses on distance correlation of antenna and waveguide in which shortening of spatial length by inserting a dielectric body between the antenna and waveguide to make the distance between waveguide and antenna ¼ wavelength so that waveguide can be installed at a practical distance with respect to the mobile phone is the main claim. However, this is the evidence of using design method according to far field condition. In addition, dielectric body having specific permittivity of 100 is used as the dielectric body having high specific permittivity in order to shorten the antenna distance described in detailed description having high dielectric loss to 1/10th because of which loss of electromagnetic waves becomes remarkably higher than the case of using dielectric body having specific permittivity of less than 5 that is generally used for shortening space in the antenna system. Thus, the claim has no feasibility and design theory based on far field fails.
Therefore, original design according to near field condition is an error of design method that uses theory based on far field condition.
The patent literature 2 uses antenna device that uses waveguide based on far field condition to reduce the electromagnetic waves absorption rate of the head while also achieving improvement in gain during the phone call. Therefore, this is not the design condition that considers conditions of head and hand.
The patent literature 3 is the constitution method of antenna that is used for both mobile phone communication and TV broadcast reception, in which far communication with base station and TV station is the target. This is also the antenna design theory based on far field condition which is not the design condition that takes into consideration the condition of head and hand.
The patent literature 4 relates to a mobile communicator that houses tip antenna, controls effect of the radiating electromagnetic waves on human body in which directional characteristics on the side opposite to human side can be strengthened. However, this is not the design according to far field condition that considers effect on human body.